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Doomsday Asteroid, The

Classroom Activity

Objective
To investigate crate force, size, and mass of objects that strike a surface through a simulation of crater impacts.

• copy of "Crater Analysis" student handout (PDF or HTML)
• a large tray or shallow pan, such as a cookie sheet
• dark sand
• flour, sugar, or another white powdered material
• a collection of "meteorites": small objects of different sizes, shapes, and masses
• a balance scale to measure the mass of each object
• a ruler
• graph paper

1. Making observations and drawing conclusions from craters gives scientists information about the force, size, and mass of the objects that strike a surface. Students can practice these skills by conducting this activity.

2. Before beginning the activity, have students move furniture out of the way, if necessary.

3. Divide the class into groups of three or four students and distribute the "Crater Analysis" student handout.

4. Within the groups, have students take on different roles: One student should drop the "meteorite," one student should make and record measurements of the "object," and the other students should crouch near the surface to make their observations. (Be sure students take care not to be hit by falling objects.)

5. After they have completed the activity, have each group exchange its surface with another group and analyze the craters. Compare the results of different groups. What variables seem to affect the shape, size, and features of a crater? What generalizations can students make about the effects of an asteroid or comet striking an Earth-like surface?

Students should recognize that almost all craters are roughly circular, regardless of the shape of the meteor or, in most cases, the angle of impact. They should also observe the following differences among craters and recognize the causes of these differences: The older craters may have smoother edges than newer craters because there is more time for motion on the surface to disturb their sharp edges. Also, older craters are often found in the area disturbed by later meteorites, so their shapes may be distorted by the newer impact. Meteorites that hit from a very low angle show a "snowplow effect," in which the sand and flour are pushed into a mound at one side of the crater. Meteorites that impact straight down will create a crater that is more even and parallel to the ground. The diameter and width of the meteorite do not affect the depth and size of the crater as greatly as do the mass and acceleration of the meteorite. To help students understand this concept, explain that the force of impact is equal to the mass of an object multiplied by its acceleration. Students may also observe that if the same object is dropped from the same angle but at a higher distance it will create a larger crater because the force of gravity makes the object increase its speed with time.